Understand Linux permission modes
- Choose File or Directory.
- Type an absolute octal mode or rwx string, or select owner, group and other permissions.
- Expand special permissions for setuid, setgid and sticky bits.
- Copy a mode or the labelled GNU command example. Commands are never executed here.
Formats, output and limits
One to four octal digits or nine permission characters with an optional matching -/d prefix; mode 0–4095. Relative commands, ACL suffixes and full ls records are unsupported. Working values stay in tab memory.
A worked example
755 is rwxr-xr-x: owner has read/write/execute; group and others have read/execute. 4755 adds setuid, giving rwsr-xr-x. 4644 instead has uppercase S because owner execute is absent.
Common questions
Is directory execute permission the same as running a file?
No. For directories it allows search/traversal. Read lists entries, while write affects entries and is constrained by other permissions and sticky-bit rules.
Does 777 guarantee my application will work?
No. It grants broad mode bits but ownership, ACLs, mounts, parents and system policy also affect access. Select a mode appropriate to your actual sharing needs.
Why does the directory command use =?
The File example uses a numeric mode, such as chmod -- 755 'YOUR_FILE'. The Directory example uses GNU chmod -- =0755 'YOUR_DIRECTORY' to explicitly request the selected special bits too. Plain numeric directory modes can preserve setuid/setgid. The equals form is a GNU extension; -- ends options before the mode and path. Replace the quoted placeholder yourself. No recursive option is included and the site runs no commands.